Thermionic device



March 25, 1930; D, c, WILKERSON 1,752,132

THERMIONIC DEVICE Filed Jan. 26,v 1924 gwuenfoc D. 6'. m'lkens'on Patented Mar. 25, 1930 UNITED STATES I DANIEL C. WILKERSON, OF WASHINGTON, DISTRICT OF COLUMBIA THERMIONIG DEVICE Application filed January 26, 1924. Serial No. 688,731.

This invention relates to an improved thermionic device of the audion type and seeks, among other objects, to provide an audion wherein the flight of the entire electronic emanation will be prescribed so that the presence of stray electrons in the tube will be eliminated and a complete. decisive and clear out control will be had in the functioning of the grid.

The invention seeks. as a further object, to provide an audion wherein, through the elimination of stay electrons in the tube, tube noises will be reduced to a minimum.

And the invention seeks, as a still further object, to provide an audion wherein by utilizing the. entire electronic output, the filament current necessary may be correspondingly reduced.

Other and incidental objects will appear hereinafter.

In the drawings:

Figure 1 is a perspective view of my improved audion, the containing vessel being broken away,

Figure 2 is an elevation partly broken away and shown in vertical section,

Figure 3 is an enlarged detail horizontal sectional view on the line 33 of Figure 2, looking in the direction of the arrows,

Figure 4 is an enlarged horizontal sectional view on the line 4-4: of Figure 2, looking in the direction of the arrows,

Figure 5 is a detail perspective view of the grid,

Figure 6 is a detail perspective View of the plate and Figure 7 is a fragmentary sectional view of the device with portions shown in elevation.

In so far as I am aware, thermionic devices of the audion type have heretofore all been constructed in such manner that the filament is exposed either at the top or bottom therer of, or at some other point, leaving an area in the field of the electronic discharge uncontrolled by the grid. In other words, the grid has not heretofore been constructed to intercept all of the electrons released or discharged from the filament. This has resulted in the 50 presence of free or stray electrons in the tube.

These stra electrons, in rebounding against the wall 0 the tube to strike the plate or return to the filament, have not only robbed the grid of a complete control of the electronic stream with a corresponding reduction in the efliciency of the audion, but, along with other causes, have tended to set up local noises in the operation of the tube. The present invention, therefore, seeks to overcome these disadvantages and, by a complete control over the entire electronic discharge, to provide an audion wherein the impulses in the grid circuit will be faithfully reproduced in the plate circuit without distortion. At the same time, the energy realized in the output is greatly augmented.

In carrying the invention into effect, I employ an evacuated containing vessel 10 which is mounted in an appropriate base 11 carrying the usual contact pins, and rising into the vessel is a stem 12. Upstanding from the stem is a support 13 over which is looped a filament or cathode 14 secured at its ends to leads 15 extendin through the stem.

Enclosing the lament 14: is a foraminous grid or control electrode 17 which may be stamped or otherwise formed from suitable sheet metal. In the present instance, I have illustrated the grid as being ellipsoidal in shape. However, the shape of the grid may be varied within certain limits provided the grid is formed to envelop the filament. At its lower end, the grid is, as shown in detail in Figure 3, formed with an opening 18 to closely accommodate the upright 13 as well as the filament leads 15 and rising from the stem is a support 19 and a grid lead 20 to which the grid is welded or otherwise secured. In the embodiment disclosed, I have shown the grid as formed of complemental upper and lower sections, the sectional construction being adopted to facilitate the mounting of the grid. As shown indetail in Figure 5, the lower section is provided with an annular flange 22 while the upper section is provided with an annular lip 23 to fit over said flange. Thus, after the lower section of the grid has been secured to the support 19 and lead 20, the upper section of the grid may be applied to cured thereto.

Enclosing the grid 17 is an ellipsoidal plate or anode 24 which, like the grid, may also be stamped or otherwise formed from suitable sheet metal. Should the shape of the grid be varied, the plate Will be varied in shape to conform thereto so that the plate will envelop the grid in uniform spaced relation. At its lower end, the plate is, as shown in detail in Figure 4, provided with an opening 25 to closely accommodatethe upright 13 and filament leads as well as smaller openings 26 to closely accommodate the support 19 and grid lead 20, and rising from the stem is a support 27 and a plate lead 28 to which the plate is welded or otherwise secured. As shown in detail in Figure 6, the plate is formed of complemental upper and lower sections so that the lower section ofthe plate may be first secured in position, when the upper section of the plate may be applied over the lower section thereof. Formed on thelower section is an annular flange 29 and formed on the upper section is an annular lip 30 to fit over said flange, the parts being Welded or otherwise secured together.

As will now be seen in view of the foregoing, the, grid 17 is shaped and mounted to 111- tercept all of the electronic emanation of the filament regardless of the direction in which such emanation may proceed and, notwithstanding the presence of the opening 18, therein, may be said to completely envelop the filament since, in practice, said opening will be but very small so that the flight of electrons therethrough will be wholly governed by the polarity of the grid. A complete control will thus be had over the entire electronic ment while the plate-envelops the grid, electrons cannot proceed from the filament to strike the wall of the containing vessel and rebound against the plate and, in fact, the presence of stray electrons in the tube will be eliminated. The control of the grid over the impulses in the plate circuit will, therefore, be

undivided with the result that impulses in the grid circuit will be exactly reproduced in the Having I claim is: v

In athermionic device the combination of an anode for controlling substantially the entire electronic emission, the surface of said anode being a surface of revolution having a major axis extending between the focii of said surface, saidanode being provided with openings, a cathode and grid enclosed by said anode, the cathode extending in a direction with said axis and lying close to said axis whereby to occupy a posltion relative to the anode such that uniformity in the spacing between the cathode and anode at all points is closely approached, supports for the cathode and grid extending through said openings, and enlargements formed on said supports and providing shields near said openings for deflecting electrons traveling in a path of escape from said anode and confining the same thus described the invention, what within the anode, the shields being enclosed DANIEL C. WILKERSON. [11.5.]-

plate circuit. Distortion and tube noises are thus eliminated while, by confining the electrons discharged so that all of said electrons must, under the control of the grid, flow directly to the plate, but small filament current will be required to secure maximum efficiency. 

